package recursivequeue;

/**
 * An implementation of a Queue using a single Stack
 * The trick is that the recursion utilizes the system stack (!)
 * 
 * @author levenick Mar 1, 2017 10:10:09 AM
 */

public class QueueImplementedAsOneStack {
    
    Stack<Integer> theStack;
    
    QueueImplementedAsOneStack() {
        theStack = new Stack();
    }
    
    boolean iEmpty() {
        return theStack.isEmpty();
    }
    
    Integer dequeue() {
        return theStack.pop();
    }
    
    void enqueue(int n) {
        if (theStack.isEmpty()) {       // if the stack is empty, simply push, and we are done!
            theStack.push(n);
        } else {                        // otherwise, pop one thing off, put it in your pocket, and *then* enqueue
            int pocket = theStack.pop();
            enqueue(n);
            theStack.push(pocket);      // push back on the thing in your pocket
        }
    }
}